1. Field of the Invention
The present invention relates generally to the fields of immunology and vaccine technology. More specifically, the present invention relates to techniques of skin-targeted non-invasive gene delivery to elicit immune responses and uses thereof.
2. Description of the Related Art
Activation of the immune system of vertebrates is an important mechanism for protecting animals against pathogens and malignant tumors. The immune system consists of many interacting components including the humoral and cellular branches. Humoral immunity involves antibodies that directly bind to antigens. Antibody molecules as the effectors of humoral immunity are secreted by B lymphocytes. Cellular immunity involves specialized cytotoxic T lymphocytes (CTLs) which recognize and kill other cells which produce non-self antigens. CTLs respond to degraded peptide fragments that appear on the surface of the target cell bound to MHC (major histocompatibility complex) class I molecules. It is understood that proteins produced within the cell are continually degraded to peptides as part of cellular metabolism. These fragments are bound to the MHC molecules and are transported to the cell surface. Thus the cellular immune system is constantly monitoring the spectra of proteins produced in all cells in the body and is poised to eliminate any cells producing non-self antigens.
Vaccination is the process of priming an animal for responding to an antigen. The antigen can be administered as a protein (classical) or as a gene which then expresses the antigen (genetic imimunization). The process involves T and B lymphocytes, other types of lymphoid cells, as well as specialized antigen presenting cells (APCs) which can process the antigen and display it in a form which can activate the immune system. Current modes for the administration of genetic vaccines has focused on invasive procedures including needle injections, scarification, and gene gun-mediated penetration. Inoculation of vaccines in an invasive mode requires equipment and personnel with special medical training, and is usually associated with discomfort and potential hazards (bleeding, infection). There is now evidence that the inoculation of vaccines in an invasive mode may be unnecessary (Tang et al., 1997; Glenn et al., 1998). Since the skin interfaces directly with the external environment and is in constant contact with potential pathogens, the immune system must constantly keep a mobilized biological army along the skin border for warding off potential infections. As a consequence, the outer layer of skin is essentially an immunocompetent tissue. Immunologic components present in the skin for the elicitation of both humoral and cytotoxic cellular immune responses include epidermal Langerhans cells (which are MHC class II-positive antigen-presenting cells), keratinocytes, and both CD4+ and CD8+ T lymphocytes. These components make the skin an ideal site for administration of vaccine. The large accessible area of skin and its durability are other advantages for applying vaccines to this tissue. Expression of a small number of antigens in the outer layer of skin without physical penetration may thus elicit a potent immune response by alarming the immune surveillance mechanism.
The efficacy of a vaccine is measured by the extent of protection against a later challenge by a tumor or a pathogen. Effective vaccines are immunogens that can induce high titer and long-lasting immunity for targeted intervention against diseases after a minimum number of inoculations. For example, genetic immunization is an approach to elicit immune responses against specific proteins by expressing genes encoding the proteins in an animal""s own cells. The substantial antigen amplification and immune stimulation resulting from prolonged antigen presentation in vivo can induce a solid immunity against the antigen. Genetic immunization simplifies the vaccination protocol to produce immune responses against particular proteins because the often difficult steps of protein purification and combination with adjuvant, both routinely required for vaccine development, are eliminated. Since genetic immunization does not require the isolation of proteins, it is especially valuable for proteins that may lose conformational epitopes when purified biochemically. Genetic vaccines may also be delivered in combination without eliciting interference or affecting efficacy (Tang et al., 1992; Barry et al., 1995), which may simplify the vaccination scheme against multiple antigens. It has been demonstrated, as presented in this application, that genetic vaccines can be inoculated in a novel way as skin-targeted non-invasive vaccines. The combination of genetic vaccines with a non-invasive delivery mode may result in a new class of xe2x80x9cdemocraticxe2x80x9d vaccines that require no special skill and equipment for administration.
While topically-applied protein-based vaccines have been studied, their usefulness may be limited. Although topical application of protein-based vaccines in conjunction with cholera toxin may also immunize animals in the same non-invasive mode (Glenn et al., 1998) as skin-targeted non-invasive genetic vaccines have already been shown to do (Tang et al., 1997), the two classes of vaccines activate the immune system via different mechanisms. Further, the efficacy of genetic vaccines is in general superior to that of protein vaccines due to the de novo synthesis of antigens similar to natural infections (McDonnell and Askari, 1996). Although U.S. Pat. No. 3,837,340 describes a method for vaccinating animals by contacting skin with dried viruses, the viruses that they employ are not genetic vectors capable of expressing transgenes. In addition, the immunogen may be protein in the viral coat, instead of protein produced from expression of viral genes in animals"" own cells.
The prior art of vaccination usually requires equipment, e.g., syringe needles or a gene gun, and special skill for the administration of vaccines. There is a great need and desire in the art for the inoculation of vaccines by personnel without medical training and equipment. A large number of diseases could potentially be immunized against through the development of non-invasive vaccination onto the skin (NIVS) because the procedure is simple, effective, economical, painless, and potentially safe. As a consequence, NIVS may boost vaccine coverages in developing countries where medical resources are in short supply, as well as in developed countries due to patient comfort. Infectious diseases caused by viruses, including AIDS and flu, by bacteria, including tetanus and TB, and by parasites, including malaria, and malignant tumors including a wide variety of cancer types may all be prevented or treated with skin-targeted non-invasive vaccines without requiring special equipment and medical personnel. The present invention satisfies this longstanding need and desire in the art.
Non-invasive vaccination onto the skin (NIVS) can improve vaccination schemes because skin is an immunocompetent tissue and this non-invasive procedure requires no specially trained personnel. Skin-targeted non-invasive gene delivery can achieve localized transgene expression in the skin and the elicitation of immune responses (Tang et al., 1997). These results indicate that NIVS is a novel and efficient method for the delivery of vaccines. The simple, effective, economical and painless immunization protocol of the present invention should make vaccination less dependent upon medical resources and, therefore, increase the annual utilization rate of vaccinations.
The present invention provides a method for immunizing animals comprising the step of skin-targeted non-invasive delivery of a preparation comprising genetic vectors, whereby the vector is taken up by epidermal cells and has an immunogenic effect on vertebrates. Also provided is a method for immunizing animals by a delivery device, comprising the steps of including genetic vectors in the delivery device and contacting the naked skin of a vertebrate with a uniform dose of genetic material confined within the device, whereby the vector is taken up by epidermal cells for expressing a specific antigen in the immunocompetent skin tissue. The genetic vector may be adenovirus recombinants, DNA/adenovirus complexes, DNA/liposome complexes or any other genetic vectors capable of expressing antigens in the skin of a vertebrate.
In one embodiment of the present invention, there is provided a method of inducing an immune response, comprising the step of: contacting skin of an individual or animal in need of such treatment by topically applying to said skin an immunologically effective concentration of a genetic vector encoding a gene of interest.
In another embodiment of the present invention, there is provided a method of inducing a protective immune response in an individual or animal in need of such treatment, comprising the step of: contacting the skin of said animal by topically applying to said skin an immunologically effective concentration of a vector encoding a gene which encodes an antigen which induces a protective immune effect in said individual or animal following administration.
In another embodiment, the invention presents a method for co-expressing transgenes in the same cell by contacting naked skin with DNA/adenovirus complexes. This protocol may allow the manipulation of the immune system by co-producing cytokines, costimulatory molecules, or other immune modulators with antigens within the same cellular environment.
The present invention also encompasses the use of a delivery device (bandages, adhesive dressings, or the like) for the delivery of skin-targeted non-invasive vaccines.
The present invention includes all genetic vectors for all of the uses contemplated in the methods described herein. Other and further aspects, features, and advantages of the present invention will be apparent from the following description of the presently preferred embodiments of the invention given for the purpose of disclosure.